Signal-controlling system



Dec. 26, 1922. 1,439,771

C. A. SPRAGUE. SIGNAL CONTROLLING SYSTEM.

FILED FEB. 27, 19?0.

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Patented Dec. 26,1922.

STATES 'PATE N 1,439,771 T OFFICE.

CLARENCE A. srEAcuE, or

ELECTRIC COMPANY, INCORPORATED, OF

NEW YORK.

SIGNAL-CONTROLLING SYSTEM.

Application filed February 27, 1920. Serial No. 361,640.

To all whom it may concern.

Be it known that I, CLARENCE A. SPRACUE, a citizen of the United States, residing at East ()range, in the county of Essex, State of New Jersey, have invented.

certain new and useful Improvements in Signal-Controlling followingis a full, clear, description. 1 y

The difficulty is often met with in signaling and similar arts that a receiver registers false signals or responses through failure to follow accurately the variations of control energy on account of the faulty action of intervening apparatus, peculiarities of the transmitting medium, disturbances originating externally of the system and kindred causes. i

Selenium, as is well known, occasions much difiiculty when employed in such systerns because of the lag of its resistance variations with respect to the'variations of intensity of illumination incident upon it. Because of this inherent lag effect of selenium, it has been found unsatisfactory for controlling a current-operated indicator or other device when the fluctuations of light to be followed are rapid. As examples of types of circuits in which this difliculty has been encountered heretofore there maybe mentioned those shown in U. S. Patents No. 900,533 to Kitsee and No. 1,320,366. to Houskee er. These are however buttwo examp es of systems which have recognized and sought to overcome the defective action of selenium. Other light- ,concise, and exact responsive substances possess similar devide simple and efiicient method and means fects.

A somewhat similar difficulty occurs in the case of transmission lines possessing distributed inductance or capacity of sufiicient amount tocause the receiver to continue to respond after the current has been' cut ofi' fromthe line at the sending station. There are doubtless other places in whicltsimilar difficulties exist but the instances cited will serve as examples ofthe troublesome eifects with which the present invention concerns itself.

This invention has for an object to pro for preventing or otherwise correcting for the defective or false response of a receiver insystems in which disturbing effects of the kind above noted are'or may be present.

Systems, of which the A feature of the invention is that the means referred to may be applied directly to existing systems and that it may be controlled to counteract to a desired degree the tendency of a responsive device to continue to register after the transmitting energy has been cut off.

The nature and objects of the invention will better be understood-from the following description in connection with the drawings in which Fig. 1 shows a curve explanatory of the action of one form of the invention, and Figs. 2, 3 and 4 illustrate diagrammatically the invention as applied to different types of circuits.

In Fig. 1, there is given a curve, characteristic of such substances as selenium, showing the relation between elapsed time (abscissae) and conductivity (ordinates) for instantaneous changes of incident energy between two fixed limiting values. The steady-state values of conductivity corresponding. to these limiting-values of incident energy are given by O and B. At time a, the incident energy is assumed to increase from its lower to its upper limit, and to remain at the upper limit until time b, when it falls to the low limit again. Intervals a to b to c, are taken as sufiiciently long to allow the conductivity selenium to reach the steady-state values B and 0 respectively. The curve representing the change in conductivity under these conditions is seen not to follow the changes in light intensity but both the decrease of conductivity lag behind the sudden increase and decrease in light intensity. Intervals c to d and (Z to e etc. represent shorter intervals but the changes in incident radiant energy are assumed be between the same limiting values as before. The conductivity curve does not fall to the value 0 or rise to B, but now has for its limits the values E and D. If the current flow through selenium correspondduring the entire time c of the the increase and device would, therefore, register tensity of the radiant energy varies and 7 tially all values.

with uniform intervals c-d, de, etc. there is a cgnductivity value such as H which lies between the extreme conductivity values assumed by the selenium element under the given conditions. If the current-controlled device responds only to currents corresponding to greater conductivity values than H, it will release for a considerable portion of the interval d-e and f-g and will indicate more or less closely the fluctuations of applied energy.

It has been assumed for simplicity that the energy fluctuations were uniform.

.While in such a case it is easier to obtain a value H which will enable a certain accuracy of' reproduction, the invention is useful in systems in which the energy variations are non-uniform both as to time and intensity The value H should be chosen high enough to intercept the curve above the highest depression point that is to be registered. If this is impractical on account of conductivity peaks of less height than the highest depression point, an average value of H is to be chosen. This will enable the energy fluctuations to be followed with much greater fidelity than-if the indicator responds to currents of substan- In Figs. 2 and 3 are shown circuit arrangements employing light-sensitive ele- 8, current -flow through the tube 7 begins ments and means according to the invention whereby the indicator responds only to currents due to desired'conductivity values.

In Fig. 2 the selenium element or other controlling element 1 is inserted in one arm of a Wheatstone bridge which is adjusted for balance when the energy applied to element 1 is of the normal steady value.

' Variations of resistance of element 1 upset the balance of the bridge and produce differences in the potential between the points 3 and 4 in the well-known manner. The external circuit between points 3 and 4 includes an interrupter 5, an indicator 6 such as a'telephone receiver, a discharge device 7, a potentiometer and polarizing battery 8. The discharge device may be of any suitable type and is shown as an evacuated chamber containing a. heated cathode 9 and a cold electrode or anode 10. By means of the potentiometer 8 the anode 10 is normally at a lower potential than the cathode 9.

No currrent flow results through the device 7, however, from this source, since the polarity is such as to oppose conduction through the discharge device. Consequently the voltage applied to the circuit from source 8 produces no indication in the receiver 6. When the potential difference between points 3 and 4 becomes great enough to exceed the opposing potential of source to take place from battery 2 and through theinterrupter 5 and indicator 6, producing a note in the receiver. No indication is produced, however, until a sufficiently large difference in potential is set up between points 3 and 4, which means that a current corresponding to some conductivity value small local current in the circuit 1, 2, 12,

produces such a large drop of potential through the resistance element 1, when the resistance of that element is high that the drop across resistance 12, and, therefore, that across the tube 7, is small. Potentiometer 8 may be adjusted to give Zero conductivity to the tube for this applied voltage. Increase of current in thelocal circuit due to increase of incident energy upon. the element 1, however, will cause a greater drop of potential across resistance 12 with resultant current transmission through the device 7 to the receiver 6. This circuit, it will be seen,'is somewhat simpler than thatof Fig. 2. Y

Fig. 4 relates to a somewhat different type of circuit from those shown in the previous figures, but shows how the invention is adapted to overcome in such a system difiiculties which are similar in their effect to those met with in the previously considered circuits. In Fig. 4, the line 13 is assumed to possess large capacity with respect to ground or with respect to the return wire, if such is used. A similar condition in effect would obtain if the line possessed large series inductance as will be understood. For convenience of considering the effect of the line capacity on the receiving relay 14 indicated at the terminal of the line, the distributed capacity of the line may all be assumed to be concentrated at 15. If a. key at the distant station (not shown) .on the line applies and removes a potential for transmitting signaling or other current, the effective capacity 15 charges and discharges alternately. If the line were .connected through the relay 14 directly to ground as by throwing switch 16 to the lower position, the relay would be slow in responding since the condenser 15 would take most of the current at first. It may be assumed, however, that the condenser charges quickly due to the impressed eleotromotive forceand the relay will be energized with slight delay. A more serious effect follows the opening of the key when the relay 14 continues to remain ener- )discharges rapidly at first through the relay, the discharge continues to some degree for a considerable length of time. This effeet is heightened due to'the fact that it takes less current to hold the relay energized than to cause it to attract its armature, or in other-words, the ratio of release to actuating current orvoltage is less than unity, this being true of all-relays of thevariable airgap type. In cases of large line capacity or of rapid actuation of the transmitting key, it is known that the relay may hold over from one impulse to the next due to the line discharge. If, however, the switch 16 is thrown to the position indicated in the drawing so as to include the discharge device 7 in series with the relay, the current flow through the relay 14 due to the discharge of the line may be made to stop after the initial rush of current upon opening the key. By keeping residual charge on the line the relay responds more quickly since less time is required after closure of the key to charge the line and the relay will release more quickly as described, since the effect of the line discharge is curbed after the current in falling reaches the strength determined by the adjustment ofthe discharge device. It will thus be seen that the voltage-operating ratio of the relay 14 is increased by the action of the discharge device 7 and the source of voltage 8. A local circuit containing a suitable receiver 17, is controlled by the relay 14.

It will be recognized from the above-described circuits that the invention is of quite general application and that still other types ofcircuits will suggest themselves to those skilled in the art, in which it may be desired to employ the invention.

Although specific circuit arrangements have been illustrated and described, they should be regarded as typical systems i1lustrative of common defects or difiiculties and the manner in which the invention is designed to overcome them and not as restricting in any sense the invention which is tobe limited only by the scope of the appended claims.

What is claimed is:

1. In a .system in which an indicator is operated in accordance With fluctuations in applied energy, means for aiding said indicater to release when the applied energy in decreasing reaches a predetermined value,

comprising a rectifier in circuit with said indicator, and a source of opposing voltage in circuit with said rectifier.

2. In a signalingcircuit, an indicator, and means for protecting said indicator from registering false signals. comprising a discharge device in circuit with said indicator for opposing the actuation of said signal and for aiding the release of said signal.

3. In a signaling system, an indicator, a

circuit for actuating said indicator, an asymmetrically conductlng device in said circuit for opposing the actuation of said indi cator and for aiding release of said indicator.

4:." In a circuit arrange ment including an energy-res )onsive device the response of which lags behind the variations in applied energy, an indicator controlled by said device, a source of energy opposing the con trol of said indicator by said device, and meansin circuit with said source for preventing energy from. said source from atfee-ting said indicator. '5. In an indicating system, a circuit containing a control element and a source of energizing current therefor, an indicator controlled by said element, a discharge device in circuit with said element, anda source of potential in circuit with said element poled normally to oppose current flow through said device.

6. In an indicating system, a circuit including'a control element, an indicator controlled thereby, means for rendering said control element e-lfective to influence said indicatoronly by current of one sign in said circuit comprising a unilaterally conducting device in circuit with said element, and means for rendering said control element effective to influence said indicator only; by current exceeding a predetermined value in said circuit, comprising a source of potential in circuit with said element and poled to oppose current-flow through said device.

7 In an indicating system, -a circuit for conveying current, an energy-responsive current-controlling element in said circuit, an indicator controlled by said element, and means for preventing current flow through said controlling element when the voltage applied to said circuit is less than a predetermined value, said means comprising a discharge device and a source of potential poled to prevent current-flow normally through said device. i

8. In a system of control, a circuit containing a source of current and means to Vary said current, a current-responsive element and a discharge device, in said circuit, and a source of voltage in said circuit poled normally to oppose current-flow through said element.

9.'In a circuit containing an energy-responsive element, means for making said &

in said circuit for aiding the response of said indicator to said current-varying means.

11. In combination, device, a source of current in circuit therewith for actuating said device, means in circuit therewith for varying said current, and a rectifier and source of opposing volt age for said rectifier in circuit with said device for aiding the response of said device to said current-varying means.

12. In an indicating system, the method of controlling the actuation of an indicator which comprises making the circuit containing said indicator conductive of ourrent-flow in only one direction, and in opposing current-fiow in said direction by interposition of a source of voltage tending to produce current-flow in the opposite direction.

13. In a system employing a control relay which initiates control upon one value of voltage being applied to said system, and releases control upon another value of voltage being applied to said system, means for causing the ratio of said values of voltage to approach unity,'comprising a discharge device in circuit with said relay, and a. source of voltage poled normally to oppose current-flow through said device.

14. A system comprising a work circuit and a control circuit therefor, a relay in the control circuit responsive to one value of voltage applied to said control circuit for a current-operated causing current to flow in said work circuit and responsive to a different value of voltage applied to said control circuit for causing current-flow in said work circuit to cease, means for varying the ratio of said voltage values one to the other comprising a discharge device in said control circuit, and a source of variable voltage poled normally to oppose current-flow through said device.

15. In an indicating system, an indicator, a circuit for controlling said indicator in response to voltage applied to said circuit, said indicator responding upon one value of voltage being applied to said circuit, and ceasing to respond upon a different value of voltage being applied to said circuit, and means for making the ratio between said voltage values approach unity, comprising a discharge device in said circuit, and a source of voltage poled normally to oppose current-flow through said device.

16. In a relay circuit, means for increasing the ratio of the release voltage of said circuit to the actuating voltage of said circuit comprising a discharge device in circuit with said relay, and a source of voltage in circuit with said discharge device poled normally to oppose current-flow through said device.

In witness whereof, I hereunto subscribe my name this 25th day of February A. D., 1920.

CLARENCE A. SPRAGUEL 

